Such a color key, as it became known, for example, from the German utility patent DE-GM 83 29 441, exhibits a body with several insertion pockets, into which color selection sticks may be inserted. The color selection sticks may, in keeping with the desires of the dental technician or the dentist, be assembled in random fashion, since the individual insertion pockets are embodied in an identical manner and no coding of the color selection sticks is undertaken to assure reception in only one particular insertion pocket or color selection pocket.
In keeping with the varied coloration of natural teeth, the necessity to offer a plurality of possible colors exists. A color selection from among, for example, 20 different colors, is practically a minimum to satisfy the needs of the patient to that extent. Now, if the individual color selection sticks are removed and held next to the natural teeth, so as to render a comparison possible in this way, the danger exists that they will not be replaced in their original color selection pocket, but rather, to another empty spot. Therefore, in the case of a color key according to DE-GM 83 29 441, a chaotic situation will arise sooner or later, due to the color sticks that are replaced together all at once.
Furthermore, as a matter of principle, it would be desirable to approach the patient with a certain preliminary selection of possible colors for the selection. For example, in many cases, there is a tendency toward the rather darker shades, toward more reddish shades, or toward lighter shades, so that the other colors are eliminated a priori.
Therefore, it has already been known how to embody the color key in modular fashion, as is provided in the case, for example, of the "Chromascop--Universalfarbschlussel" [Chromascope Universal Color Key] made by the firm of Ivoclar AG. In this process, 4 similar colors that are assembled in a common carrier that is coded according to a basic color, are stored, summarized on the color key. To this end, the color key exhibits corresponding recesses for the interchangeable reception of a plurality of carriers, so that there already exists a certain freedom of arrangement.
Furthermore, it has even been suggested that several color keys be coupled to one another in order to facilitate dealing with larger dolor keys. This solution, however, entails a rather complex creation of color keys of this type, even though, basically, the disadvantages of the color key according to the aforementioned utility patent are not eliminated.
Basically, various possibilities exist for the classification of mixed colors. One possibility resides in using lightness as a basis, and summarizing one color group each, thus, colors having an emphasis in a particular underlying color, by means of similar combinations of numbers or letters. Mixed colors between various groups of colors, can then be designated by intervening combinations of numbers or letters.
The precise designation of the colors is very important, since only by means of definite identification is it assured that the dental technician uses the right teeth. Faulty designations can give rise to the production of faulty dentures that can no longer be used.
Currently, there are, among others, the Kerascop color designation key, and the Chromascop designation key. Assignment of the most important of these colors to both color designation keys may be accomplished by means of the following table:
______________________________________ 110 01 120 1A 130 2A 140 1C 210 2B 220 1D 230 1E 240 2C 310 3A 320 5B 330 2E 340 3E 410 4A 420 6B 430 4B 440 6C 510 6D 520 4C 530 3C 540 4D ______________________________________
From this overview, it becomes apparent that on the basis of the various points of view according to which tooth colors may be classified, a purely linear arrangement of colors does not, by its nature, do justice to the differences. The structure of color categorization that is afforded by the known color keys is therefore, basically, too rigid to be able to be used for all conceivable schemes of classification, and to that extent, it represents a compromise.